Difference between revisions of "Messages Format"

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(S-Ppprzlink v1.0)
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The overhead is 16 bytes (4 bytes of counter, 12 bytes of tag), plus the necessary key exchange at the beginning of communication.
 
The overhead is 16 bytes (4 bytes of counter, 12 bytes of tag), plus the necessary key exchange at the beginning of communication.
  
===S-Ppprzlink v1.0===
+
===S-Pprzlink v1.0===
 
  PPRZ-message: ABCxxxxxxxDE
 
  PPRZ-message: ABCxxxxxxxDE
 
     A PPRZ_STX (0x99)
 
     A PPRZ_STX (0x99)

Revision as of 17:55, 31 August 2017

Introduction

Messages Format and how to use them

For the message definitions see http://docs.paparazziuav.org/latest/paparazzi_messages.html

Types

Paparazzi "PPRZ" standard message for direct serial connection

Pprzlink v1.0

PPRZ-message: ABCxxxxxxxDE
    A PPRZ_STX (0x99)
    B LENGTH (A->E)
    C PPRZ_DATA
      0 SENDER_ID
      1 MSG_ID
      2 MSG_PAYLOAD
      . DATA (messages.xml)
    D PPRZ_CHECKSUM_A (sum[B->C])
    E PPRZ_CHECKSUM_B (sum[ck_a])

Pprzlink v2.0

Note that there is currently no explicit way to recognize whether the protocol is v1.0 or 2.0 so it has to be known before the communication.

PPRZ-message: ABCxxxxxxxDE
    A PPRZ_STX (0x99)
    B LENGTH (A->E)
    C PPRZ_DATA
      0 SOURCE (~sender_ID)
      1 DESTINATION (can be a broadcast ID)
      2 CLASS/COMPONENT
        bits 0-3: 16 class ID available
        bits 4-7: 16 component ID available
      3 MSG_PAYLOAD
      . DATA (messages.xml)
    D PPRZ_CHECKSUM_A (sum[B->C])
    E PPRZ_CHECKSUM_B (sum[ck_a])


Secure Paparazzi (S-PPRZ) for serial and transparent modem communication

The overhead is 16 bytes (4 bytes of counter, 12 bytes of tag), plus the necessary key exchange at the beginning of communication.

S-Pprzlink v1.0

PPRZ-message: ABCxxxxxxxDE
    A PPRZ_STX (0x99)
    B LENGTH (A->E)
    C PPRZ_DATA
      0-3 COUNTER
      // ciphertext start
      4 SENDER_ID
      5 MSG_ID
      6 MSG_PAYLOAD
      . DATA (messages.xml)
      // ciphertext end
      7-18 TAG (12 bytes)
    D PPRZ_CHECKSUM_A (sum[B->C])
    E PPRZ_CHECKSUM_B (sum[ck_a])

S-Pprzlink v2.0

In this case we decrypt only packets with matching DESTINATION (or broadcast), to avoid decrypting unwanted data.

PPRZ-message: ABCxxxxxxxDE
    A PPRZ_STX (0x99)
    B LENGTH (A->E)
    C PPRZ_DATA
      0 SOURCE (~sender_ID)
      1 DESTINATION (can be a broadcast ID)
      2-5 COUNTER (4 bytes)
      // ciphertext start
      6 CLASS/COMPONENT
        bits 0-3: 16 class ID available
        bits 4-7: 16 component ID available
      7 MSG_PAYLOAD
      . DATA (messages.xml)
      // ciphertext end
      8-19 TAG (12 bytes)
    D PPRZ_CHECKSUM_A (sum[B->C])
    E PPRZ_CHECKSUM_B (sum[ck_a])




XBee API format

XBee-message: ABCDxxxxxxxE
    A XBEE_START (0x7E)
    B LENGTH_MSB (D->D)
    C LENGTH_LSB
    D XBEE_PAYLOAD
      0 XBEE_TX16 (0x01) / XBEE_RX16 (0x81)
      1 FRAME_ID (0)     / SRC_ID_MSB
      2 DEST_ID_MSB      / SRC_ID_LSB
      3 DEST_ID_LSB      / XBEE_RSSI
      4 TX16_OPTIONS (0) / RX16_OPTIONS
      5 PPRZ_DATA
        0 SENDER_ID
        1 MSG_ID
        2 MSG_PAYLOAD
        . DATA (messages.xml)
    E XBEE_CHECKSUM (sum[D->D])

   ID is AC_ID for aircraft, 0x100 for ground station

Telemetry storage format for data logger

TLM-message: ABCDEFGHxxxxxxxI
    A PPRZ_STX (0x99)
    B LENGTH (H->H)
    C SOURCE (0=uart0, 1=uart1, 2=i2c0, ...)
    D TIMESTAMP_LSB (100 microsecond raster)
    E TIMESTAMP
    F TIMESTAMP
    G TIMESTAMP_MSB
    H PPRZ_DATA
      0 SENDER_ID
      1 MSG_ID
      2 MSG_PAYLOAD
      . DATA (messages.xml)
    I CHECKSUM (sum[B->H])